package service

import (
	"context"
	"time"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// ReportingRollupService computes daily/weekly/monthly rollup aggregations
// from raw ReportingEvents. Reference: Chatwoot app/services/reporting_events/rollup_service.rb (81行)
//
// Rollup computation:
//   1. Group raw events by (account_id, date, dimension_type, dimension_id, metric)
//   2. Compute COUNT, SUM(value), SUM(value_in_business_hours) per group
//   3. Upsert into reporting_events_rollups table
type ReportingRollupService struct {
	eventRepo  *repository.ReportingEventRepo
	rollupRepo *repository.ReportingEventsRollupRepo
}

// NewReportingRollupService creates a new rollup service.
func NewReportingRollupService(eventRepo *repository.ReportingEventRepo, rollupRepo *repository.ReportingEventsRollupRepo) *ReportingRollupService {
	return &ReportingRollupService{eventRepo: eventRepo, rollupRepo: rollupRepo}
}

// ComputeDailyRollup computes rollup for a specific account and date.
func (s *ReportingRollupService) ComputeDailyRollup(ctx context.Context, accountID uint, date time.Time) error {
	startUTC := time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, time.UTC)
	endUTC := startUTC.Add(24 * time.Hour)

	// Get raw events for this time range
	events, err := s.eventRepo.FindByAccountIDAndTimeRange(ctx, accountID, startUTC, endUTC)
	if err != nil {
		applogger.L().Errorf("ComputeDailyRollup find events: %v", err)
		return err
	}

	if len(events) == 0 {
		return nil // No events to rollup
	}

	// Build rollup rows using the backfill logic
	rollupRows := s.buildRollupFromEvents(accountID, date, events)

	// Delete existing rollups for this date and replace
	if err := s.rollupRepo.DeleteByAccountAndDate(ctx, accountID, date); err != nil {
		applogger.L().Errorf("ComputeDailyRollup delete old: %v", err)
		return err
	}

	if len(rollupRows) > 0 {
		if err := s.rollupRepo.BulkCreate(ctx, rollupRows); err != nil {
			applogger.L().Errorf("ComputeDailyRollup bulk insert: %v", err)
			return err
		}
	}

	return nil
}

// ComputeRollupForRange computes daily rollups for a date range.
func (s *ReportingRollupService) ComputeRollupForRange(ctx context.Context, accountID uint, since, until time.Time) error {
	for d := since; !d.After(until); d = d.AddDate(0, 0, 1) {
		if err := s.ComputeDailyRollup(ctx, accountID, d); err != nil {
			applogger.L().Errorf("ComputeRollupForRange date=%s: %v", d.Format("2006-01-02"), err)
		}
	}
	return nil
}

// GetSummaryMetrics retrieves aggregated metrics for a given time range and dimensions.
// Returns metrics matching Chatwoot's summary report API response format.
func (s *ReportingRollupService) GetSummaryMetrics(ctx context.Context, accountID uint, since, until time.Time, dimensionType model.DimensionType, dimensionID uint) (map[string]float64, error) {
	rollups, err := s.rollupRepo.FindByAccountAndDateRangeWithDimension(ctx, accountID, since, until, dimensionType, dimensionID)
	if err != nil {
		return nil, err
	}

	metrics := make(map[string]float64)
	for _, rollup := range rollups {
		metricKey := string(rollup.Metric)

		def := GetReportMetricDefinition(metricKey)
		if def == nil {
			// Unknown metric, still record
			metrics[metricKey] = float64(rollup.Count)
			continue
		}

		switch def.AggregateType {
		case "count":
			metrics[metricKey] = float64(rollup.Count)
		case "average":
			if rollup.Count > 0 {
				metrics[metricKey] = rollup.SumValue / float64(rollup.Count)
			}
		case "average_biz":
			if rollup.Count > 0 {
				metrics[metricKey] = rollup.SumValueBusinessHours / float64(rollup.Count)
			}
		case "sum":
			metrics[metricKey] = rollup.SumValue
		}
	}

	return metrics, nil
}

func (s *ReportingRollupService) buildRollupFromEvents(accountID uint, date time.Time, events []model.ReportingEvent) []model.ReportingEventsRollup {
	// Group events by (dimension_type, dimension_id, raw_metric_name)
	type groupKey struct {
		dimType model.DimensionType
		dimID   uint
		metric  model.RollupMetric
	}

	groups := make(map[groupKey]*RollupAggregate)
	dims := BackfillDimensions

	for _, event := range events {
		for _, dim := range dims {
			dimID := accountID
			if dim.GroupColumn == "user_id" && event.UserID != nil {
				dimID = *event.UserID
			} else if dim.GroupColumn == "inbox_id" && event.InboxID != nil {
				dimID = *event.InboxID
			}

			key := groupKey{dimType: dim.Type, dimID: dimID, metric: model.RollupMetric(event.Name)}
			agg, ok := groups[key]
			if !ok {
				agg = &RollupAggregate{
					DimensionType: dim.Type,
					DimensionID:   dimID,
					Metric:        model.RollupMetric(event.Name),
				}
				groups[key] = agg
			}
			agg.Count++
			agg.SumValue += event.Value
			agg.SumBizHours += event.ValueInBusinessHours
		}
	}

	// Expand each group into rollup metrics
	var rollupRows []model.ReportingEventsRollup
	for _, agg := range groups {
		rollupMetrics := ExpandEventToRollupMetrics(agg.Metric, agg.Count, agg.SumValue, agg.SumBizHours)
		for rm, data := range rollupMetrics {
			rollupRows = append(rollupRows, model.ReportingEventsRollup{
				AccountID:              accountID,
				Date:                   date,
				DimensionType:          agg.DimensionType,
				DimensionID:            agg.DimensionID,
				Metric:                 rm,
				Count:                  data.Count,
				SumValue:               data.SumValue,
				SumValueBusinessHours:  data.SumBizHours,
			})
		}
	}

	return rollupRows
}